Along with the rapid development of new energy automobiles, the requirements on the performance of an entire car, such as dynamics property, smoothness and driving range, continuously increase. In order to satisfy such requirements, the new energy power driving system must have an automatic transmission.
Presently, the automatic transmissions of new energy automobiles mostly choose to make improvements on the basis of automatic transmissions of traditional internal combustion engine automobiles. Four traditional automatic transmissions, namely, hydraulic automatic transmissions (AT), continuously variable transmissions (CVT), electrically controlled mechanic automatic transmissions (AMT) and double clutch automatic transmissions (DCT), are all used in the field of new energy automobiles.
However, these transmissions have too many shift positions, which affects the efficiency and reliability of the system. Moreover, they are relatively large and expensive, and not suitable for new energy automobiles. In the future, two-speed, three-speed or four-speed transmission will be the mainstream of new energy automobiles. Presently, the gear shifting actuating mechanisms of two-speed transmissions are electrical, pneumatic or hydraulic, which increases the cost and volume of the system, and decreases the reliability of the system to some extent.